Circuit breaker employing high and low intensity gas blast



July 22, 1952 JANSSON 2,604,563

CIRCUIT BREAKER EMPLOYING HIGH AND LOW INTENSITY GAS BLAST Filed Oct. 3,1949 war/170212100115 W/WVAI/I/I/YA Patented July 22, 1952 CIRCUITBREAKER EMPLOYING HIGH AND LOW' INTENSITY GAS BLAST Gustav, E. Jansson,North Quincy, Mass, assignor to Allis-Chalmers Manufacturing Company, -Milwaukee, Wis, a corporation of Delaware Application- October 3, 1949,Serial No. 119,372

'6 Claims. '1,

This invention: relates to circuit interrupting devices and. moreparticularly to are extinguishing means for usein connec-tion therewith.Spe cifically thisinvention is. an improvement on the inventiondisclosed and claimed in George A. Burnhams application, Serial No.126,572, filed November 19,1949; and Gustav E. Janssons application,Serial No. 119,373, filed October 3, 1949.

In the construction and operation of circuit intcrrupters, it isfrequently necessary to provide means for extinguishing quickly the arewhich is drawn between separable arcing contacts. This are isusuallyblown by blowout means, such as an air blast, into an arc chutewhich is arranged to quench thearc .bylengthening it, cooling it,or-otherwise.

The interruptingcapacity of a circuit breaker interrupter in a highvoltage circuit depends to a. great. extent on the circuitcharacteristics relating to the. rate of increase of recovery voltagewhen the current is interrupted. Although the breaker may be. successfulin interrrupting the currentmomentarily, the. recovery voltage acrossthe interrrupting gap, may rapidly rise to such a. value that arcing isreestablished before the breaker has sufficiently increased thedielectric strength of the gap. For interrupting higher currents undersuchv conditions, it would be necessary toilmrease the pressure and thein.- tensity of the gas blast. If it is impractical to increase the gaspressure, the size of the blast passage or'the type of gas passage. orpassages must be varied toprovide-for greater gas volume orreater.interruptingability. Such changes, however, usually result, ineither a more expensive or larger breaker.

In accordance with the, invention claimed an arc, chute is providedadjacent a. pair of arcing contacts for receiving the arc atone endthereof and exhausting the arcing products at the other end thereof. Thearcchute comprises a first blast passage for interrupting relatively.high currents and a second blast passage for interrupting relatively lowcurrents. An insulating blast divider is arranged between the. source offluid under pressure and the arc chute of the circuit breaker fordistributing the blast from the point where it arrives in highlyconcentrated form to the arcingz' ones. This blast divider comprises afunnel-shaped portion'for receiving th blast o fl fro th v s r nd a pa rof passages or nozzles foredividing theblast into a high intensitystream which flows through the first blast passage for interrupting highcurrents and a low intensity stream which flows through the second biastpassage for interrupting lower currents. I -he nozzle for directing thehigh, n e si y. s r m. i o h irst s a s e is asymmetrical at its intakeportion and symmetrical at its outlet portion. The nozzle for directingthe low i-ntensity streamintothe second blast passage may beasymmetrical throughout its entire length. 13y inserting a suitableresistor in the circuit by means of the arc in the first blast passage,the voltage recovery'rate of the current is decreased, and if thecircuit isnot interrupted by the high, intensity blast, itmay beinterrupted at a greatly decreased current at a much more favorablerecovery rate by the cornparatively limited blast of the low intensitystream in the second; blast passage. In this manner, the interruptingcapacity of the circuit breaker, for a given blast; pressure and gasconsumption, is greatly increased.

It is, therefore, one object of the present invention to provide a newand improved arc interrupting device.

Another object of this invention is to provide a new and improved gasblast circuitinterrupter which divides a blast of gas into a highintensity stream and a low intensity stream, the high intensity streamflowing through a passage for interrupting a relatively high current andthe low intensity stream flowing through a different passageforinterrupting a current of relatively low magnitude.

A further object of the invention is to provide a new and improved arcextinguishing device for interrupting a resistor-shunted are by means ofa stream of gas and a predetermined time thereafter extinguishing asecond arc in series with the shunting resistor by means of anotherstream of gas.

Objects and advantages other than those above set forth will be apparentfrom the following description when read in connection with theaccompanying drawing in which Fig. 1 is a diagrammatic showing partly incross section of a fluid blast circuit breaker em: bodying thepresentinvention;

Fig. 2 is a view in cross section of the. embodimentillustrated Fig. 1taken along the line II..II;

Fig. 3 is. a cross sectional view of the embodiment illustrated Fig.1taken along the. line II a Fig. l is across sectionalview of Fig. 1taken along theline IVIV.

The cross blast type air blast circuit breaker shown by way of examplein Fig. 1 comprises relatively movable arcing contacts such as fixedcontact structure I of the finger type and a pivoted blade-like contact8. The fixed contact structure may comprise a plurality of currentcarrying contacts and an arcing contact as is well known, and iselectrically connected to one line terminal 9 of the breaker. Theblade-like movable contact is connected to the other line terminal I0.Although in general, circuit breakers of the type considered in Figs. 1,2, 3 and 4 are provided with a plurality of similar pole structures, onefor each phase of a polyphase electric circuit, only one such polestructure is shown in the drawing and the circuit breaker will bedescribed in detail as if it were of the single pole unit type.

The movable contact 8 is suitably connected to an actuating mechanism(not shown) through a connecting rod II for operating the movablecontact between closed and open circuit positions.

For the purpose of extinguishing the arc formed between the contactswhen a power circuit connected thereto is opened, an insulating arcextinguishing structure I2 is arranged with respect to the contacts sothat the arc is drawn at the entrance of the structure directly oppositea gas blast supply conduit I3. The conduit I3 is suitably connectedthrough a blast valve (not shown) to a source of compressed gas, such asair, comprising for example a storage tank and compressor equipment (notshown).

The are extinguishing structure may, for example, define a double barrelarc chute I4 comprising a first blast passage I5 for interruptingrelatively high currents and a second blast passage I6 arranged parallelwith and spaced apart from passage I5 for interrupting relatively lowcurrents. The blast passages l5 and I6 as illustrated in Fig. 3 havesubstantially uniform cross sections which may be rectangular orcircular in form.

An insulating blast divider I9 is arranged between the gas supplyconduit I3 and the arc chute I4 for distributing the blast from thepoint where it arrives in highly concentrated form by the narrow blastsupply conduit l3 to an arc chamber provided for enclosing the are uponinception thereof. The are chamber comprises arcing zones and 2I whichare spaced apart and situated at the upstream end of the double barrelarc chute I4. The blast divider comprises a funnel-shaped portion 22mounted immediately adjacent the supply conduit I3 and a pair of nozzles23 and 24 which diverge from the diverging end of portion 22 towardchute passages I5 and I6.

The sides of the funnel-shaped portion 22 diverge at such a rate thatthe air expansion within the funnel is limited to the required minimum.The common axis 25 of supply conduit I3 and of funnel-shaped portion 22of blast divider I9 is situated only slightly to the right of axis 26 ofthe first blast passage I5 of arc chute I4. Thus, the air blast reachingthe downstream end of funnel-shaped portion 22 may pass into nozzle 23with little restriction.

Nozzle 23 comprises an inlet portion 21 and an outlet portion 28. Theinlet portion 21 may be asymmetrical and the outlet portion 28symmetrical. Nozzle 23 may have a zone of minimum cross sectional areabetween the upstream and the downstream ends thereof and the walls 29may converge more rapidly on the upstream end thereof than they divergeon the downstream end thereof, thus providing a well defined point ofmaximum fiow velocity where the rate of deionization of the arc path ishigh and the rate of fluid expansion downstream from the point ofmaximum flow velocity is controlled. Outlet portion 29 of nozzle 23forms with the Wall of the first blast passage I5 a circular air pocketor gap 30.

Nozzle 24 comprises an inlet portion 3I and an outlet portion 32. Asindicated in Fig. 3, the inlet and outlet portions 3| and 32,respectively, provide an oblong cross sectional area.

The width of nozzle 24 is constant throughout its length and is greaterthan the width of nozzle 23 at its narrowest point. Nozzle 24 provides azone of minimum cross sectional area between the inlet and outlet endsthereof.

As illustrated in Figs. 1 and 4 the fixed contact structure I projectsalmost to the longitudinal axis of nozzle 23 and is therefore subjectedto an intense air blast upon operation of the arc extinguishingstructure.

The walls of the funnel-shaped portion 22 of the blast divider I9, asillustrated in Figs. 1, 2 and 4, define a diverging passage 35therethrough which accommodates the movable sickleshaped blade contact8. These walls closely surround contact 8 and control the escape ofcompressed air and are products through passage 35 into blast passagesI5 and I5. Passage 35 is provided with a plurality of transversalgrooves 36 which tend to establish eddies in the small flow of escapingair and are products through passage 35. These eddies, in turn, tend tominimize the rate of that fiow.

A pair of probe electrodes 31 and 38 may be mounted within blastpassages I5 and I6, respectively, for aiding arc extinguishment.Electrodes 31 as illustrated in Fig. 2 may comprise a rectangularportion 39 of refractory metal or alloy which is mounted to extendacross the full width of the first blast passage I5 at the downstreamend of outlet portion 28 of nozzle 23. A current limiting resistor 40interconnects electrode 31 and the multiple finger contacts of the fixedcontact structure I, thus lowering the value of the arc current at apredetermined time during arc extinguishment. Electrode 38 may comprisea rectangular portion H of refractory metal or alloy which is mounted toextend across the full width of the second blast passage IB at thedownstream end of outlet portion 32 of nozzle 24.

The circuit breaker illustrated in the drawing is shown with thecooperating arcing contacts in the closed circuit position. An openingoperation is initiated by admission of gas under pressure to supplyconduit I3. The further flow of such gas through passage 35 offunnel-shaped portion 22 of blast divider I9 is at first impeded bycontact 8, which obstructs the passage 35. Actuation of the connectingrod II moves blade contact 8 toward the right to open the electriccircuit.

As the blade contact 8 is separated from the fixed contact I an arc isdrawn across the arcing zone 20 leading to the first blast passage I5and substantially concurrently therewith a path is opened for a blast ofgas of high intensity through the supply conduit I3 and nozzle 23 ofblast divider I9 to the first blast passage I5. This blast includessubstantially all the gas being supplied through conduit I3, and drivesor loops the are from zone 20 into passage I5. Frequently the arc isinterrupted in the first blast passage y the blast. of asflowing throughnozzle 2.3. As theiblade continues. to. move toward: the right, thearcisextended intozonezl if. it isnotalready extinguished. The-second blastpassage It and nozzle, 24 of blast divider I9. are'uncovered. and partof the arc isdriven or. looped fromzone 2| into blast passage l 6 by,theblastirom'nozzle.24.

In accordance with the inventionclaimed a funnel-shaped portion 22 ofblast divider 19 forms a blast duct, the side, walls of which diverge ata rate suchthat the air expansion within the blast. ductv isv limitedto. a predetermined minimum value. The. blast therefore reaches thevarcing. zoneat. a hi h pressure, that has a strong tendency toovercome,the back pressure produced. by the; heat generated. by theparc. Thecommon axis of conduit 13 and. funnelshaped portion. 22. of blastdivider I9 is situated slightly. to the right of the axis of the, first.blast passage l50 f.arc chute, l;4.. This isconduciveto suchadistributionof the blast of air; that, most of it is caused to escapethrough. hefirst blast assage [5 which is situated immediately adiacent.the station ry fin r icontactsil while nly a m r p rtion of the blastis.caused o scape through the second blast passage 1 6 which is situated ata point remote from the stationary finger contacts 1.

This concentration of the blast in, the form of a high intensity streamon thestationary arcing contact structure 15 causes an intensedeionization of the arc path at the point'where a. reignition is mostlikely to occur. The concentration of the blast upon arcing zone 20 andthe first blast passage l5 causes a rapid rise of the resistance of theportionof thearc situated at the upstream end of the blast passage. I5,The are rises and comes incontact with probe electrode 31. The sectionof the'arc which is shunted by resistor 40 interconnecting the fixedfinger contact structure I with the probe electrode 3'! arranged in thefirst blast'passagel5 wi1lbc rapidly extinguished and replaced after thefirst current zero by current through theresistor 40. From then on inthe interrupting cycle, the task is limited to interrupting a resistorlimited are current of lower intensity and this may be. achieved eitherat the upstream end of'blast. passage, l5. or at the upstream endsof'the first and second blast passages l5 and 16, respectively.

By providing rectangular shaped probe electrode portions 39 and 4|extending across the full width of blast passages l5 and I6respectively, the arc when driven into passages 15 and I6 cannot bypassthe electrodes 31 and 38 without being engaged by them. Thus, the fullarc extinguishing effect of the probe electrode is assured.

The intensity of the blast of gas necessary to interrupt a resistorlimited current of low intensity is much lower than that necessary tointerrupt a higher are current. Therefore, a blast of gas of relativelylow intensity is provided through blast passage [6 for interruptinglower currents. The lower intensity of such blast results both from thedivision of the blast into two streams through nozzles 23 and 24 and ofthe arrangement of nozzle 24 out of axial relation with supply conduitI3, whereby the momentum of the blast forces it to flow principallythrough nozzle 23. If the arc is not interrupted in blast passage 15 bythe high intensity stream provided by nozzle 23 of blast divider 19 theresistor limited current is then interrupted in blast passage l6 by a,lower intensity blast of gas provided by nozzle 24.

Gap 30 formed by the outlet portion 28 of nozzle-1:3: and; the.upstream. portion. of: blast pas.- sage. li rormsa circular airpocketwhichis. not likely to be contaminated; by arc'products; and thustends tojprecludeanelectrlc breakdown between .the first and secondblast passagesv l5 and I6, respectively.

Although. but oneembodiment of' the present invention hasbeenillustrated and described, it will be apparent to those skilled intheart that various changes and modifications maybe; madetherein'without departing-'iromthespirit of the invention or from thescope of the appended claims.

It isclaimed and desired 7 to secure by Letters Patent:

1 In. a fluid blast circuit interrupter, the combination comprising; a,source of, fluid under pressure, separable arcing contacts forestablishing anarc, a conduit for conveying a blast of fluiidrrom saidsource adjacent saidcontacts for extinguishing the are drawn uponseparation, of said contacts, an arc chute mounted adjacent saidcontacts-for receivingthe are at: one end thereof and; exhausting thearc; products at the other end. said are chutecomprisia first: blastpassage and; a second: blastapassa and: a blast divider mountedbetweensaid conduit and said arcchute comprlsinga first nozzle; having acircular cross sectional; area between the ends thereof for directing a:highintensity stream of fluid un er pressure: into. said firs blestr paa for interrupting:relatively high currents anda second nozzle having:an oblong cross. sectional area bctweenwthe'ends thereof for directing alower intensity stream of fluid under pressure into said second blast,passage for interrupting relatively; lowcurrents. I

2. In; a. fluid, blast: circuit interrupter, the; combinationcomprisingz; asource offluid under pressure, separablev arcing-contactsforestablishing a.n.arc,.a. conduit foraconveying-a blast of fluid from.saidsource-adjacent said contactsfor extinguishing the are drawn, uponseparation of saidcontacts, an arc; chute mounted adjacent said"contacts for receiving the are at one end thereof-ianda exhausting the;are products at the other end, said: arc chute comprising a first blastpassage. and a second: blast passage, and: a. blast divider mountedbetween. said conduit and said are chute comprising a first nozzlehaving a circular cross sectional area between the ends thereof fordirecting a high intensity stream of fluid under pressure into saidfirst blast passage for interrupting relatively high currents and asecond nozzle having an oblong cross sectional area between the endsthereof for directing a lower intensity stream of fluid under pressureinto said second blast passage for interrupting relatively low currents,said cross sectional area of said second nozzle being substantiallysmaller than said cross sectional area of said first nozzle.

3. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, separable arcing contacts forestablishing an arc, a conduit for conveying a blast of fluid from saidsource adjacent said contacts for extinguishing the arc drawn uponseparation of said contacts, an arc chute mounted adjacent said contactsfor receiving the arc at one end thereof and exhausting the arc productsat the other end, said are chute comprising a first blast passage and asecond blast passage, and a blast divider mounted between said conduitand said are chute comprising a first nozzle having a circular crosssectional area between the ends thereof for directing a high intensitystream of fluid under pressure into said first blast passage forinterrupting relatively high currents, and a second nozzle having anoblong cross sectional area between the ends thereof for directing alower intensity stream of fluid under pressure into said second blastpassage for interrupting relatively low currents, said second nozzlehaving a cross sectional area substantially smaller than said crosssectional area of said first nozzle and providing a zone of minimumcross sectional area between the ends thereof.

4. In a fluid blast circuitinterrupter, the combination comprising: asource of fluid under pressure, separable arcing contacts forestablishing an arc, a conduit for conveying a blast of fluid from saidsource adjacent said contacts for extinguishing the are drawn uponseparation of said contacts, an arc chute mounted adjacent said contactsfor receiving the are at one end thereof, said are chute comprising afirst blast passage for interrupting relatively high currents and asecond blast passage for interrupting relatively low currents, and ablast divider mounted between said conduit and said are chute comprisinga first nozzle having a fluid intake portion and a fluid outlet portionfor directing a high intensity stream of fluid under pressure into saidfirst blast passage for interrupting relatively high currents and asecond nozzle for directing a lower intensity stream of fluid underpressure into said second blast passage for interrupting relatively lowcurrents, said first nozzle being asymmetrical at its fluid intakeportion and symmetrical at its fluid outlet portion.

5. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, separable arcing contacts forestablishing an are, a conduit for conveying a blast of fluid from saidsource adjacent said contacts for extinguishing the are drawn uponseparation of said contacts, an arc chute mounted adjacent said contactsfor receiving the are at one end thereof, said are chute comprising afirst blast passage for interrupting relatively high currents and a 4fluid outlet portion for directing a high intensity stream of fluidunder pressure into said first blast passage for interrupting relativelyhigh currents and a second nozzle for directing a lower intensity streamof fluid under pressure into said second blast passage for interruptingrelatively low currents, said outlet portion of said first nozzleforming with said first blast passage a gap which prevents an electricbreakdown between said first and second blast passages.

6. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, separable arcing contacts forestablishing an arc, a conduit for conveying a blast of fluid from saidsource adjacent said contacts for extinguishing the are drawn uponseparation of said contacts, an arc chute mounted adjacent said contactsfor receiving the are at one end thereof and exhausting the are productsat the other end, said are chute comprising a first blast passage and asecond blast passage, a pair of proble electrodes mounted one withineach of said blast passages and each comprising a metallic portionextending across substantially the full width of said blast passages forengaging the arc, a current limiting resistor conductively connectingsaid probe electrode mounted within said first blast passage to one ofsaid separable arcing contacts, and a blast divider mounted between saidconduit and said arc chute comprising a first nozzle of circular crosssection for directing a high intensity stream of fluid under pressureinto said first blast passage for interrupting relatively high currentsand a second nozzle of oblong cross section for directing a lowerintensity stream of fluid under pressure into said second blast passagefor interrupting relatively low currents.

GUSTAV E. JANSSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,290,004 Thommen July 14, 19422,290,708 Rankin July 21, 1942 2,306,240 Wyman Dec. 22, 1942 2,365,134Amer et al Dec. 12, 1944

